An Israeli field hospital, where wounded Syrians are treated, is seen a top a ridge overlooking a Syrian villages, close to the ceasefire line between Israel and Syria, in the Israeli-occupied Golan Heights September 9, 2013.

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Jerusalem — Part of a series of articles looking at the regional interests at stake in Syria's civil war. The full list is on the left of your screen.

Though Syria has technically been at war with Israel for decades and has long pressed for the return of the Golan Heights, which Israel captured in the 1967 war, the government of President Bashar al-Assad has long been one of Israel’s quietest and least aggressive enemies.

At several junctures, most recently in 2008, Israel nearly concluded a peace deal with Mr. Assad, who would have become only the third Arab leader to sign such an agreement.

So in the early stages of Syria’s civil war, some Israelis quietly hoped Assad would retain power, preferring a known quantity over the potential for a Sunni militant regime rising to power, particularly one with links to Al Qaeda.

However, Israel is deeply concerned by Assad’s support for Hezbollah, the Lebanon-based Shiite militant movement whose proclaimed raison d’être is fighting Israel. Both Syria and Iran have cultivated Hezbollah as an ally that could pummel Israel with its vast supply of weaponry, which is believed to include long-range missiles that could hit Tel Aviv. Israel has a strong interest in the Iran-Syria-Hezbollah “axis of resistance” becoming weaker or destroyed altogether.

At this point, the ideal outcome in Syria from the Israeli point of view is a drawn-out war, in which Assad’s forces continue to battle the rebels, weakening both sides and reducing the threat that either poses to Israel. Israel has so far stayed out of the civil war, except for four attacks on Syrian weapons stores, intended to prevent their suspected transfer to Hezbollah. Assad has refrained from any counterattacks.

Though Israel has prepared for possible fallout from the fighting, which has already spilled into neighboring Lebanon, most Israeli security experts tend to agree that Assad is likely to use restraint if he launches a retaliatory attack in the wake of a US strike.

"I think [Assad] understands that the meaning of attacking Israel might have very severe consequences to [his] ability to continue his regime,” says Maj. Gen. Gadi Shamni, who recently retired from a long career in the Israel Defense Forces, most recently as defense attaché in Washington.

The worst-case scenario for Israel would likely be Assad either turning his chemical weapons capabilities on Israel in a last-ditch move of desperation, or losing control of them to Sunni militants who could then direct them toward Israeli targets.

But a broader Israeli concern is that Iran will become emboldened by the lack of decisive Western action on Syria, and that the US in particular will be too distracted or too lacking in credibility to effectively address what Israel sees as the biggest regional threat: an Iranian nuclear bomb.